The gas tank is under the seat in my 39. I installed a sediment bowl where the fuel line comes out under the cab. The sediment bowl has a shut off valve. The fuel line goes from there to an electric fuel pump then to the mechanical pump. The electric fuel pump has a toggle switch under the dash. I use the electric pump when the truck has been sitting for awhile. I started to get a lot of debris in the sediment bowl, so I installed a new gas tank. This set up has worked well over the years.
Rick
